T-Butyl hydroperoxide alters fatty acid incorporation into erythrocyte membrane phospholipid

Abstract

Because the ability of cells to replace oxidized fatty acids in membrane phospholipids via deacylation and reacylation in situ may be an important determinant of the ability of cells to tolerate oxidative stress, incorporation of exogenous fatty acid into phospholipid by human erythrocytes has been examined following exposure of the cells to t-butyl hydroperoxide. Exposure of human erythrocytes to t-butyl hydroperoxide (0.5–1.0 mM) results in oxidation of glutathione, formation of malonyldialdehyde, and oxidation of hemoglobin to methemoglobin. Under these conditions, incorporation of exogenous [9,10- 3H]oleic acid into phosphatidylethanolamine is enhanced while incorporation of [9,10- 3H]oleic acid into phosphatidylcholine is decreased. These effects of t-butyl hydroperoxide on [9,10- 3H]oleic acid incorporation are not affected by dissipating transmembrane gradients for calcium and potassium. When malonyldialdehyde production is inhibited by addition of ascorbic acid, t-butyl hydroperoxide still decreases [9,10- 3H]oleic acid incorporation into phosphatidylcholine but no stimulation of [9,10- 3H]oleic acid incorporation into phosphatidylethanolamine occurs. In cells pre-treated with NaNO 2 to convert hemoglobin to methemoglobin, t-butyl hydroperoxide reduces [9,10- 3H]oleic acid incorporation into phosphatidylcholine by erythrocytes but does not stimulate [9,10- 3H]oleic acid incorporation into phosphatidylethanolamine. Under these conditions oxidation of erythrocyte glutathione and formation of malonyldialdehyde still occur. These results indicate that membrane phospholipid fatty acid turnover is altered under conditions where peroxidation of membrane phospholipid fatty acids occurs and suggest that the oxidation state of hemoglobin influences this response.